1. Field of Invention
This invention relates generally to drilling fluid additives and specifically relates to the packaging of the additives in a sweep cartridge which allows the insertion of the additive and the cartridge directly into the drilling operation by way of one of the drill pipes or the kelly pipe.
2. Description of Prior Art
During the course of drilling a well it is often advantageous to circulate concentrated amounts of drilling fluid additives, known as slugs, through the drill hole to obtain certain specific benefits such as flocculation of the drilled solids, stabilization of the bore hole and cleaning of the bore hole among others. The introduction of the slug of additive into the pipe is known as a drill pipe sweep.
When possible, a very effective means of introducing a small amount of concentrated additive is to simply pour the additive directly into the open drill string after the kelly pipe has been removed and while making a connection of another drill pipe to the drill string. When introduced in this manner, the additive is then pumped, by the normal pumping operation, down the drill string and back up the annulus between the drill string and the wall of the bore hole as drilling is resumed.
Utilization of this drill pipe sweep technique, of introducing additives into the system has very often been prevented by the U-tubing effect of the lighter fluids inside the drill string being forced to back-flow up through the drill string due to the somewhat higher density of the drilled solids-laden fluid in the annulus. As the kelly pipe is removed from the drill string prior to attaching the next drill pipe, water backflows out of the drill string until the pressures equalize. This results in a loss of time in the drilling operation should it be desired to introduce additive at this point into the drill string.
Generally it is not economically feasible to delay drilling operations by waiting for the back-flow of water to cease to allow space for additives to be poured into the drill string. The U-tubing effect can be prevented by using drill string floats or flapper check valves but operational limitations which these devices pose frequently prohibit their use since their application impedes pressure readings.
Even at best, a few minutes of valuable rig time is consumed in waiting for back-flow to cease and some degree of inconvenience is experienced in the process of pouring drilling fluid additives directly into the drill string during connection of the next drill pipe to the drill string. The cost of rig time has been estimated at Three Thousand Six Hundred Dollars ($3600) per day and drilling additives may be introduced into the system approximately forty-eight times during a 1500 ft. drilling day. If it takes approximately two minutes per connection and the back-flowing takes approximately ten minutes to equalize, then it can be readily seen how a better way of introducing additives to the system will be economically feasible if downtime can be minimized.
For a more detailed background on well drilling, the reader is referred to a booklet entitled, "A Primer of Oil Well Drilling," second edition issued by the University of Texas and the American Association of Oilwell Drilling Contractors, filed herewith as prior art. Other drilling methods are taught in the U.S. Pat. No. 4,473,124 issued on Sept. 25, 1984 to J. G. Savins.
The before mentioned drilling fluid additives are typified in the various U.S. Pat. No. 4,571,422 issued Feb. 18, 1986 to K. C. Symes et al; U.S. Pat. No. 4,063,603 issued Dec. 20, 1977 to J. J. Rayborn and U.S. Pat. No. 4,514,308 issued Apr. 30, 1985 to R. L. Clampett et al. Other additives are shown in the commercial literature by Nalco Chemical Company (Nalco brand ASP-700) and Allied Colloids Company (Alcomer brand 120L). All of the above are filed herewith as prior art.
It is known to introduce drilling fluid additives in the well bore by using a self-contained device as taught in the U.S. Pat. No. 4,191,254, issued on Mar. 4, 1980 to K. E. Baughman et al. This device is dropped down into the drill string and distributes additives after which the device dissolves or is forced through the orifices in the drill bit. The device is then ground up into tiny pieces which are carried on with the drilling mud. A similar concept is taught in the U.S. Pat. No. 4,611,664 issued on Sept. 16, 1986 to M. G. Osterhoudt III et al.
The lowering of a drilling fluid additive into the well bore by a device is taught in the U.S. Pat. No. 4,706,753, issued on Nov. 17, 1987 to K. Ohkochi et al. A weight is dropped onto the device to destroy the bottom plate of the device thereby releasing the fluid additives. The dropping of explosives into a bore hole is taught in the U.S. Pat. No. 3,986,430 issued on Oct. 19, 1976 to D. L. Coursen et al.
It is also known to use a device to restore lost circulation in a well as taught in the U.S. Pat. No. 3,362,476, issued Jan. 9, 1968 to H. K. van Poollen. Water soluble bags are filled with circulation-restoring materials which are lowered into the bottom of the well to react with fluid in the well-bore. In a similar manner, pellets have been used for water restoration as taught in the U.S. Pat. No. 2,836,555, issued on May 27, 1958 to A. L. Armentrout.
An arrangement for full hole drilling using a hole wall former which is lowered into the drill string in the vicinity of the drill bit is taught in the U.S. Pat. No. 4,378,050, issued to R. A. Tatevosian et al on Mar. 29, 1983.
Planar surfaces which are rupturable such as polystyrene are known in the art and are used in various applications such as covers for trays and are taught in the U.S. Pat. No. 3,916,076 issued Oct. 18, 1975 to F. E. Eastes.
The introduction of drilling fluid additives can also be accomplished in other places in the water pumping system of the drilling operations with various results in order to keep downtime at the drill rig to a minimum. However it is preferable to make a sweep or introduction of additive at every drill pipe connection and it would be best to do this at the connection of the drill pipe or at the kelly pipe. Drilling fluid additives such as flocculants and bore hole stabilizing polymers can be introduced into a clear water drilling operation at the pump suction or at the flow line as well as directly into the drill string.
Dripping liquid polymer into the suction tank probably improves hole stability and helps flocculate drilled solids during the one to two hours that a five gallon bucket lasts, but contributes little if any to hole cleaning.
Mixing a quart or so of liquid polymer in a chemical barrel and allowing it to drip into the drill water as it returns to the reserve pit flocculates drilled solids very well, but contributes nothing to hole cleaning or stability.
A drill pipe sweep on every pipe connection will provide a substantial degree of hole cleaning, hole stability and drilled solids flocculation. With this technique liquid polymer additions are made almost continuously or at frequent intervals and in direct proportion to the penetration rate.